Conventional fire extinguishers have required heavy metal containers holding liquids under high pressures often with gauges to indicate the interior pressure. Such containers have to utilize heavy gauge metal to prevent explosions as the heat increases the liquid pressures, and the extinguishers are consequently heavy and expensive. The use of plastic containers for individual fire extinguishers has not been considered feasible because of the danger of explosions caused by increased internal pressure when subjected to heat.
Automatic sprinkler systems with heat-activated release valves have been provided but these require an expensive system of supply piping and are often not practical for protecting special locations.
It has been proposed to utilize as an individual fire extinguisher a tube or container of thermoplastic resin which melts or softens at a predetermined temperature, the tube being filled with pressurized extinguisher liquid which is discharged at the point the tube is opened. The tube may be conformed to and located within an object to be protected such as a television set. Such a tube or container would not be satisfactory as fire protection for a waste receptacle as the direction of the discharge of extinguisher liquid would not be controlled and might be directed away from the flames in the receptacle.
It has been further proposed to provide an individual fire extinguisher having the extinguisher liquid contained in a thin flexible envelope rupturable by a predetermined heat and/or pressure, but the envelope necessarily has been encased in a rigid outer shell for protection and either the shell must allow access to the envelope to subject it to the exterior heat to rupture the envelope and discharge the extinguisher liquid at the proper time, or an exposed fusible sealing member has been provided for the envelope. Here, again, the direction of discharge of the extinguisher liquid is not adequately controlled.